Climate scientists are warning that the benefits of fracking are largely illusory. Tom Wigley of the National Center for Atmospheric Research in Boulder, Colorado, concluded in a recent study that substituting gas for coal increases rather than decreases the rate of warming for many decades.
Burning coal releases sulphur dioxide and black carbon. These cool the climate, offsetting up to 40 per cent of the warming effect of burning coal.
Fracking, which involves pumping water at high pressure into shale beds to release trapped gas, also leaks methane into the atmosphere. Methane is a far more potent greenhouse gas than CO2 and switching from coal to gas could only bring benefits this century if leakage rates get below 2 per cent. If rates are at 10 per cent, the top end of current US estimates, the gas would deliver extra warming until the mid-22nd century.
A recent review by the UN Environment Programme concluded that emissions from fracking and other unconventional sources of natural gas could boost warming initially, and would only compare to coal over a 100-year timescale.